1. Field of the Invention
The present invention relates to a thin-film magnetic head for a rigid magnetic disk drive (RDD), which includes a slider body formed of ferrite and which exhibits relatively low inductance.
2. Discussion of the Prior Art
As one kind of magnetic head of air-bearing or flying type for a rigid magnetic disk drive (RDD), there is known a so-called thin-film magnetic head including a slider body having air bearing portions on its surface on which a magnetic recording medium is slidable, and a head portion consisting of thin films formed on a trailing end face of each of the air bearing portions. Referring to FIG. 1 showing an example of thin-film magnetic head of this type, a slider body 2 has a pair of rail-shaped air bearing portions 4, 4 formed on its surface on which a magnetic recording medium is slidable. The air bearing portions 4, 4 have a suitable width, and extend in parallel with each other in the direction in which the recording medium slides. On the trailing end face (i.e., rear end face as viewed in the sliding direction) of each of the air bearing portions, there is formed a thin-film head portion which includes upper and lower magnetic poles 6, 6 in the form of thin films, and a thin-film coil 8 interposed between the magnetic poles 6, 6. Leads 10, 10 are connected to the opposite ends of the coil 8 so that a suitable electric current may be applied to the coil 8 through the leads 10, 10.
In the thin-film magnetic head as described above, the slider body 2 is generally formed of a material such as CaTiO.sub.3 or Al.sub.2 O.sub.3 -TiC. The slider body 2 formed of CaTiO.sub.3 has a high coefficient of friction with respect to a magnetic disk (magnetic recording medium), and therefore has a high tendency of damaging the magnetic disk due to the frictional contact, whereby the slider body itself is likely to be damaged. The slider body 2 formed of Al.sub.2 O.sub.3 -TiC has a poor sliding characteristic with respect to the magnetic disk, and therefore has a high tendency of damaging the magnetic disk. Where the air bearing portions 4, 4 of the slider body 2 have peculiar configuration, such as a bridging structure as in a negative-pressure type magnetic head slider, or a shaped rail structure, such configuration must be usually achieved by an ion-etching method, which pushes up the cost of manufacture of the head due to an expensive installation for the etching operation and relatively slow etching speed.
In view of the above, it has been proposed that the slider body of the thin-film magnetic head is formed of a magnetic material consisting of ferrite that has an excellent sliding property with respect to a magnetic recording medium such as a magnetic disk. Some examples of magnetic heads using the ferrite material are disclosed in JP-A-54-27415 and JP-A-57-123516, wherein a non-magnetic material such as glass is embedded in a groove(s) formed in a ferromagnetic substrate such as ferrite, so that upper and lower magnetic poles are spaced a suitable distance apart from each other by the non-magnetic material, so as to enhance the operating efficiency of the magnetic head. However, this type of magnetic head cannot enjoy some advantageous features of the conventional thin-film magnetic head, since the ferrite substrate (slider body) serves as one of the magnetic poles (lower magnetic pole). Namely, when a bulk material such as ferrite is used as a magnetic pole, the inductance of the obtained magnetic head is undesirably increased, compared to when the magnetic poles consist only of thin films. Thus, the magnetic head of the above type fails to exhibit low inductance that is a typical feature of the thin-film magnetic head.
Another example of the magnetic head using the ferromagnetic substrate is disclosed in JP-A-61-156508, wherein a thin-film head portion consisting of upper and lower magnetic layers and coil are formed on the ferromagnetic substrate such as ferrite. Conventionally, the magnetic head of this type suffers from magnetic flux leakage from the upper magnetic layer toward the ferromagnetic substrate having a relatively large width, resulting in an undesirably increased track width. To avoid this, the magnetic head disclosed in the above-identified publication is constructed such that its portion in the vicinity of the magnetic gap (where the magnetic disk slides) is filled with a suitable non-magnetic material, so that the magnetic flux leakage occurs between the upper and lower magnetic layers. Nonetheless, the thus constructed magnetic head also suffers from relatively high inductance, since the lower magnetic pole consists of the lower magnetic layer and ferromagnetic bulk body.